Generally, a bit line precharge circuit in a semiconductor memory device precharges a pair of bit lines to a half of a power supply voltage VCC during a bit line precharge operation. In a precharge operation, it is important to maintain the precharge voltage level of the pair of the bit lines to a half of the power supply voltage VCC in the semiconductor memory device.
In a case that the precharge voltage of the pair of the bit lines is higher than a half of the power supply voltage VCC, the data margin deteriorates at a high voltage level and, in a case that the precharge voltage of the pair of the bit lines is lower than a half of the power supply voltage VCC, the data margin deteriorates at a low level. That is, in a state where the pair of bit lines are precharged to a half of a power supply voltage VCC, a charge sharing operation between the pair of the lines is carried out when a word line connected to a memory cell is selected in an active operation. At this time, in a case that a bit line sense amplifier amplifies a high-level data on the pair of the bit lines when the precharge voltage level is higher than a half of the power supply voltage VCC, the high-level data on the pair of the bit lines cannot be amplified to a sufficient voltage level of the power supply voltage VCC or the amplification cannot be carried out exactly. Similarly, in a case that a bit line sense amplifier amplifies a low-level data on the pair of the bit lines when the precharge voltage level is lower than a half of the power supply voltage VCC, the low-level data on the pair of the bit lines cannot be amplified to a sufficient voltage level of a ground voltage or the amplification cannot be carried out exactly.
Conventional semiconductor memory devices precharge bit lines using a precharge circuit included in a bit line sense amplifier. However, with increase in a level of integration in semiconductor devices, a resistance of bit lines increases and the features of bit line precharge deteriorate because of such an increased resistance.